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The Sound of Shapes

The ability of some humans to determine the pitch of a musical note in the absence of a reference note ("perfect pitch") has been a favorite topic in Science Frontiers (SF#99, #102, and #111). It now seems that the human ear-brain combination can also discern the shapes and dimensions of thin, vibrating plates by the sound they make.

In one type of experiment, conducted by A.J. Kunkler-Peck (Brandeis University) and M.T. Turvey (University of Connecticut), subjects gave surprisingly accurate estimates of the heights and widths of three different vibrating plates. The plates were concealed behind a screen, but the subjects could remotely control a striker. In further experiments, other subjects could distinguish between the sounds of circular, rectangular, and triangular plates.

(Anonymous; "Listen to the Shapes," Science News, 157:171, 2000.)

Comment. We all know from experience that small, thin plates produce higher pitched sounds that larger plates. How-ever, the ability to assign accurate dimensions without some training is surprising. The same can be said for the identification of shapes. Who, for ex-ample, has been exposed to vibrating, triangular-shaped plates in ordinary life? Could we be dealing here with another innate talent that, like perfect pitch, seems to have no adaptive value in the evolution of humans?